Invisible neutrino decays at the MOMENT experiment

Abstract

We investigate invisible decays of the third neutrino mass eigenstate in future accelerator neutrino experiments using muon-decay beams such as MuOn-decay MEdium baseline NeuTrino beam experiment (MOMENT). MOMENT has an outstanding performance to measure the deficit or excess in the spectra caused by neutrino decays, especially in $ν_μ$ and $\barν_μ$ disappearance channels. Such an experiment will improve the constraints of the neutrino lifetime $τ_3$. Compared with exclusion limits in the current accelerator neutrino experiments T2K and NOvA under the stable $ν$ assumption, we expect that MOMENT gives the bound of $τ_3/m_3\ge1.46\times10^{-11}$~s/eV at $3σ$ confidence level, which is better than their recent limits: $τ_3/m_3\ge 7\times10^{-13}$~s/eV in NOvA and $τ_3/m_3\ge 1.41\times10^{-12}$~s/eV in T2K. The non-decay scenario is expected to be excluded by MOMENT at the $>3σ$ confidence level, if the best fit results in T2K and NOvA are confirmed. We further find that reducing systematic uncertainties is slightly more important than the running time. Finally, we find very little correlations between $τ_3/m_3$ and other oscillation parameters, which point to an advantage of MOMENT to measure $τ_3/m_3$.

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